1. Field of the Invention
The present invention relates generally to a printer, and more specifically, to a duplex printer capable of printing on the first and second planes of a sheet of recording paper.
2. Description of the Related Art
A duplex printer with a switch back mechanism is being provided.
U.S. Pat. No. 4,978,980 discloses a method of minimizing an entire time period required for printing in the duplex mode in a duplex printer including a switch-back mechanism, a face up tray, and a face down tray. More specifically, a method of obtaining hard copies of sheets of recording papers in the order of the pages each for the minimum time period by printing the sheets in the order of the pages represented by: EQU 1.fwdarw.3.fwdarw.2.fwdarw.5.fwdarw.4.fwdarw.7.fwdarw.6.fwdarw.9.fwdarw.8.f wdarw.10,
when the sheets are discharged onto the face up tray, while by printing in the order of the pages represented by: EQU 2.fwdarw.4.fwdarw.1.fwdarw.6.fwdarw.3.fwdarw.8.fwdarw.5.fwdarw.10.fwdarw.7. fwdarw.9,
when the sheets are discharged onto the face down tray.
The face up tray is a tray for accommodating sheets of recording paper with images already formed thereon, with the first plane facing upward in the one-side mode and with the second plane facing upward in the duplex mode. This is for the purpose of obtaining hard copies in the order of the pages in the duplex mode, but the tray should be attached to the side of a printer for discharging a sheet of recording paper in a manner as stated above, making it difficult to install the printer in a small space.
The face down tray in contrast is a tray for accommodating with the first plane side facing downward in the one side mode and with the second plane side facing downward in the duplex mode. This is for the purpose of obtaining hard copies in the order of the pages in the one-side mode, and the tray is of a structure which can be placed on the top of casing of printer, thereby permitting placing of the printer even in a small space.
In a printer, an image is formed on a sheet of recording paper based on image data read out from a memory. Memory storage capacities are different among printers of different kinds, and even among printers of the same kind, memory storage capacities are different when memories are additionally provided as options.
A method disclosed in Japanese Patent Laying-Open No. 63-313172 requires a storage capacity for 2 pages when a face up tray is used, and requires a storage capacity for 3 pages when a face down tray is used. Accordingly, if the memory does not have a necessary storage capacity, duplex printing cannot be conducted.